Posted on 10/13/2016 11:34:58 AM PDT by BenLurkin
[A] Los Alamos National Laboratory research team demonstrates an important step in taking quantum dot, solar-powered windows from the laboratory to the construction site by proving that the technology can be scaled up from palm-sized demonstration models to windows large enough to put in and power a building.
"We are developing solar concentrators that will harvest sunlight from building windows and turn it into electricity, using quantum-dot based luminescent solar concentrators," said lead scientist Victor Klimov. Klimov leads the Los Alamos Center for Advanced Solar Photophysics (CASP).
Luminescent solar concentrators (LSCs) are light-management devices that can serve as large-area sunlight collectors for photovoltaic cells. An LSC consists of a slab of transparent glass or plastic impregnated or coated with highly emissive fluorophores. After absorbing solar light shining onto a larger-area face of the slab, LSC fluorophores re-emit photons at a lower energy and these photons are guided by total internal reflection to the device edges where they are collected by photovoltaic cells.
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In the Nature Energy paper, the team reports on large LSC windows created using the "doctor-blade" technique for depositing thin layers of a dot/polymer composite on top of commercial large-area glass slabs. The "doctor-blade" technique comes from the world of printing and uses a blade to wipe excess liquid material such as ink from a surface, leaving a thin, highly uniform film behind. "The quantum dots used in LSC devices have been specially designed for the optimal performance as LSC fluorophores and to exhibit good compatibility with the polymer material that holds them on the surface of the window," Klimov noted.
LSCs use colloidal quantum dots to collect light because they have properties such as widely tunable absorption and emission spectra, nearly 100 percent emission efficiencies, and high photostability (they don't break down in sunlight).
(Excerpt) Read more at phys.org ...
Sounds very cool. But why restrict it to windows? Seems any sunlit surface will do.
From the article, it sounds like they need the glass’s internal reflections to transport the photons to the window’s edges - something not doable on a roof shingle, for instance.
Good by another couple trillion dollars in tax money to pay for this. It can only provide a minuscule amount of electricity consumed in an office. We’re talking a few light bulbs. There is only so much you can harvest from sunlight. It doesn’t matter if you have 100% efficient solar collectors. The sun only puts out so much light and you can’t change that.
"After absorbing solar light shining onto a larger-area face of the slab, LSC fluorophores re-emit photons at a lower energy and these photons are guided by total internal reflection to the device edges where they are collected by photovoltaic cells. "
Those re-emitted photons travel through the glass and are collected at the edges of the glass by photovoltaic cells.
Can't do that with solid brick, or wood.
Thanks I didn’t understand that part.
I see, said the blind man, as he picked up his hammer and saw.
Yeah, I thought the “device edges” were the photovoltaic dots themselves, not the glass. Oh well, it’s still cool because the efficiency is supposedly 100% (which seems to violate the laws of physics, but whatever...)
Yeah, I thought the “device edges” were the photovoltaic dots themselves, not the glass. Oh well, it’s still cool because the efficiency is supposedly 100% (which seems to violate the laws of physics, but whatever...)
True, but the solar intensity varies quite a bit. In the areas where the added power from these collectors would be handy are likely to be ones where A/C is heavily used. Conveniently, the panels put out the most power when A/C use it highest. Diverting some of that radiant energy helps cool things as well.
On a sunny day, we crank out kWs from our 17 roof panels, far more than we use. Somoneone in the PNW, no way.
Now my question is this: though they claim great efficiency, there was a bit in there about ‘lower power’ photons ultimately hitting the photovoltaic cells... which sounds a lot like a loss of efficiency to me. Never mind that the cells themselves are still gonna be only ~30-40% efficient.
However, if they can redirect light to the edges... along with the associated heat... then there’s also a fair chance of making these windows much more thermally efficient - which would save power along with generating some.
Like cold fusion, this technology will be commercially viable in no more than ten years for at least the next 25 years.
Well. if you put the glass over those shingles it would still collect the photons. The pane of glass can be any size, one can cover more than a single shingle. And, you can leave walkways between the glass panels for maintenance.
The more blue the light, the more energy. Solar conversion is like a pole vault in that the light has to be of high enough energy to make it over the threshold (band gap). Unlike the sport though, it’s best to just make it over the pole. Anything in excess just produces heating; and, too low produces no electricity at all.
The sunlight is absorbed by a florescent material which emits a less blue single frequency of light into the glass pane. The color (frequency) is matched to a device (photo-voltaic) which can absorb all the light and convert it to electrical energy.
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